Winding shaft

ABSTRACT

The invention relates to a shaft axle for winding up a material web, particularly plastic films, namely particularly stretch films. In order to provide a shaft axle with a strength and stiffness as high as possible, a shaft axle is provided showing a shaft body, which is made largely from fiber-reinforced plastic to yield bending stiffness as high as possible, and cavities, provided along the exterior perimeter of the shaft body, with the cavities being limited in the radial interior direction by a layer of fiber-reinforced plastic and allowing tension bars to expand from the cavities radially towards the outside.

The invention relates to a shaft axle for winding a material web, particularly plastic films, and here particularly stretch films. Additionally, the invention relates to a method for producing such a shaft axle as well as a winding device comprising such a shaft axle.

Winding shafts, comprising a shaft axle and a winding core for winding up and/or unwinding web-shaped, tape-shaped, or string-like materials of very different kinds, for example paper, aluminum, and plastic films, textiles, or fleece-like webs or the like, are widely known and designed particularly for the respective purpose for use and/or the specific winding technique applied.

The acceptance of the winding core in an appropriate winding device occurs commonly via expanding tension bars and/or tension pads with a mechanic or pneumatic control, causing a central stress of the winding core and allowing driving of the winding core even with strong torque.

Particular requirements of the winding core also arise during the winding up of stretch films.

Stretch films—depending on the respective application, also loading unit/safety film, pallet stretch film, winding stretch film, or packaging stretch film—are indispensable in modern logistics for the transportation of goods loaded on pallets. In addition to securing the pallets, such films also protect the goods on the pallet from exposure to weather and soiling. Here, the stretch film adjusts optimally to the shape of the pallet and the products without damaging them.

Additionally, in the meantime various semiautomatic or automatic stretching facilities for “stretch-wrapping” the pallets with the goods located thereon have become available for the application of the stretch film.

Stretch films are produced in most different thicknesses and widths. Typically, for example, film thicknesses are from 12-35 μm with a width of the roll from 200 mm to 1,000 mm, preferably 500 mm, which are wound onto rolls weighting 10-20 kg.

With presently approximately 1.5 million tons annually within Europe alone and approx. 3.0 million tons per year globally the market of stretch films will be of substantial volume in the future as well. The requirements set for the equipment for the production of stretch films are therefore steadily increasing with regards to efficiency and output. These increasing demands must be met by the winding device, which winds up the produced, finished stretch film onto a winding core at the end of the production facility. Here, a winding core may be used over the entire production width. Usually, however, several winding cores are used side-by-side, with the stretch film then prior to being wound onto the winding cores being divided in the direction of production by knives aligned appropriately. This way, for example, at a production width of 1,500 mm, here three application widths of 500 mm each are produced parallel and wound up.

The winding cores themselves are generally made from a cardboard tube and may be very different, depending on the application, with regards to width, interior diameter, and exterior diameter, and thus also with regards to their wall thickness.

In order to allow winding up the produced stretch film on the winding core for all applications, the respective winding device shows a shaft axle with adjustable tension pads for a radial clamping of the respective winding cores. However, since it is not known in advance what kind of winding cores will be placed upon the shaft axle, the shaft axle must be designed to accommodate all potential types of applications. Simultaneously it must be observed that the stretch film to be wound up shows great elasticity of up to 400%, due to the features described above. This leads to extreme requirements set for the shaft axle.

A winding device is known from WO2013/003968 A9, in which the shaft axle is supported at both sides in a double bearing, in order to prevent any undesired vibrations of the shaft axle and simultaneously allows high circular accelerations.

In order to yield high bending stiffness for the shaft axle with a simultaneously low external diameter, it is also known to produce the shaft axles entirely or partially from fiber-reinforced composite materials, as described for example in WO 2005/124212 A1 or in U.S. Pat. No. 5,746,387.

Shaft axles made from fiber-reinforced composite materials are commonly made from plastic or a cross-linked resin material (reaction resin), which comprises reinforcing fibers, for example natural fibers, fiberglass (FBE=fusion bonded epoxy material) or carbon fibers (CFL=carbon fiber laminate), in the form of sections of a final length, continuous fibers, fleece or webs. Composite materials with fibrous sections are particularly extruded continuously or processed by extrusion molding. Composite materials with continuous fibers are particularly processed in winding processes (filament winding) or by way of pultrusion in order to form tubes or sheaths.

CFRP shafts (=carbon fiber reinforced plastic) are particularly suited. Here, CFRP regularly comprises aligned continuous fibers, which are embedded in a plastic matrix, usually in several layers. The recesses required for the tension bars, however, reduce the strength and stiffness of the shaft axle in an undesired fashion.

The objective of the invention is therefore to provide a shaft axle with a strength and stiffness as high as possible.

This objective is attained in a shaft axle for winding up a material web, comprising a shaft body, made largely from fiber-reinforced plastic to yield bending stiffness as high as possible, and showing cavities, which are provided along the external perimeter of the shaft body, with said cavities being limited in the radial interior direction by a layer made from fiber-reinforced plastic and allowing tension bars to extend in the radial exterior direction out of the cavities.

An essential acknowledgement of the invention comprises that the cavities for the tension bars are not made from radially continuous recesses but are limited in the radial interior direction by a layer of fiber-reinforced plastic. This way, the strength and stiffness of the shaft axle can be effectively increased.

According to a preferred embodiment it is provided that the fiber-reinforced plastic is made from aligned continuous fibers, which are connected via cured resin.

According to another preferred embodiment it is provided that the aligned continuous fibers are made from carbon fibers.

According to another preferred embodiment it is provided that the tension bars show at their radial end cup-shaped elements, which are made from plastic and/or a fiber-reinforced material.

A potential method for producing the shaft axle according to the invention is a method in which formed bodies are provided for accepting tension bars that can radially expand, around which continuous fibers are layered, with the formed body in the radial internal direction resting on at least one layer comprising aligned continuous fibers, in which the formed bodies together with the continuous fibers are connected via a cured resin, and in which after the curing of the resin the radially expandable tension bars are inserted into the formed bodies.

The formed bodies may be made from aluminum or plastic, for example. In order to allow the formed bodies to sit fixed in their fittings, to the extent possible, the formed bodies may, in addition to the holding strength of the resin, also be adhered and/or screwed in.

Another method for producing the shaft axle according to the invention is a method in which for the purpose of yielding a bending stiffness as high as possible a shaft body is produced largely from fiber-reinforced plastic, with cavities being cut into the shaft body along the perimeter, with said cavities being limited in the radial interior direction by a layer made from fiber-reinforced plastic, and tension bars being inserted in the cavities that can radially expand.

The winding device for winding up a material web with a shaft axle according to the invention preferably represents a winding device with a bearing arrangement located at least at one side of the shaft axle, in which the respective end of the shaft axle is supported in two sections distanced from each other.

According to a preferred embodiment, bearing arrangements are provided at both sides of the shaft axle, with the ends of the shaft axle resting therein, with each of the two bearing arrangements supporting the corresponding end of the shaft axle in two areas distanced from each other.

According to another preferred embodiment, at least one winding core is provided encompassing the shaft axle, which can be fixed in reference to the shaft axle via the expanding tension bars.

The advantages of the invention are overall higher strength and stiffness of the shaft axle as well as its support, allowing permanently higher production speeds due to a higher rotation critical for bending.

Further details and advantages of the invention are described based on the attached drawings. Here it shows:

FIG. 1 a winding shaft with a disadvantageous alignment of the cavities in reference to the continuous fibers,

FIG. 2 a winding shaft with an alignment of the cavities to diagonally extending continuous fibers,

FIG. 3 a winding shaft with an alignment of the cavities towards axially extending continuous fibers,

FIG. 4 the support of a shaft axle at both sides via double bearings, and

FIG. 5 a cross-section through a shaft axle according to the invention.

At first, the alignment of the cavities is described in reference to the continuous fibers.

When the shaft axle is produced with continuous fibers in a winding process (filament winding), it must be observed that a parallel alignment of the continuous fibers in reference to the axis is not possible due to the limitations of the machines provided for the production of the winding core. Rather, only an alignment up to approx. 7° in reference to the axial direction is possible. If now, as shown in FIG. 1, the recesses of the cavities are still aligned axially, then this has negative influences upon the strength and stiffness of the shaft axle due to the intersecting continuous fibers.

FIG. 1 shows the left half of a winding shaft with a shaft axle 101. The winding shaft shows axially aligned cavities 102, into which the tension bars can be inserted, which can be pressed pneumatically towards the outside and optionally can be retracted again by a spring force. The alignment of a first layer of continuous fibers is indicated by 103 and the alignment of a second layer of continuous fibers inside the shaft axle by 104. Due to the fact that the cavities shorten the continuous fibers 103 and 104, this alignment of the cavities has negative influences upon the strength and stiffness of the shaft axle.

FIG. 2 shows a winding shaft with a shaft axle 201 and with an alignment of the cavities towards diagonally extending continuous fibers. The reference characters 201, 203, and 204 are equivalent to the reference characters 101, 103, and 104, so that in this regard reference can be made to the description of FIG. 1. However, the cavities 202 are aligned here along the direction of the continuous fibers 204 so that said negative influence upon the strength and stiffness of the shaft axle can be reduced.

FIG. 3 shows a winding shaft with a specially produced shaft axle 301, as known for example from WO 2005/124212 A1. The reference characters 301 and 302 are equivalent to the reference characters 101 and 102 of FIG. 1, so that in this regard reference can be made to the description of FIG. 1. The shaft axle is here produced such that the aligned continuous fibers 303 extend axially in reference to the shaft axle 301 and to the axially aligned cavities 302. This is possible according to WO 2005/124212 A1 by the use of reinforcing ribs, which were produced in a pultrusion method and which allow a particularly high content of fiber volume.

The cavities are therefore aligned accordingly as well.

FIG. 4 shows the support of a shaft axle with double bearings at both sides, as known from WO 2013/003968 A9. WO 2013/003968 A9, however, fails to disclose the combination of a double bearing with a shaft axle made from fiber-reinforced plastic. This combination is also particularly advantageous in the point of view of the invention. The shaft axle 401 produced from CFRP is clamped fixed at the left side in the double bearing 402. The bearing arrangement 403 is also embodied as a double bearing, however, this bearing arrangement is detachable via two-armed pliers so that one or more winding cores can be pushed from the right onto the shaft axle and/or can be removed therefrom again, after the pliers unit has pivoted away the bearing arrangement 403.

FIG. 5 shows a cross-section through a shaft axle according to the invention of fiber-reinforced plastic. The shaft axle 501 shows five cavities distributed over its perimeter, in which the pneumatic tubes 502 as well as articulate tension bars 503 are inserted. The cavities are limited in the radial interior direction by a layer of fiber-reinforced plastic, so that the desired stiffness of the shaft axle is yielded. Optionally, but not necessarily, the tension bars 503 are additionally pre-stressed with spring elements which move the tension bars into the position shown in FIG. 5a as soon as sufficient air has been removed from the hoses 502. If the tension bars 503 are not pre-stressed, the tension bars 503 are in a position between the respective stops when air has exhausted, without it here being possible to transmit any torque upon the winding core located at the outside.

If now, based on the condition according to FIG. 5 a, the hoses 502 are filled with compressed air, the condition according to FIG. 5b develops, according to which the tension bars 503 are extended and can apply a radial force upon the winding core located at the outside.

The tension bars 503 may extend continuously in the axial direction over the entire shaft axle. Alternatively it is also possible that the tension bars are made from several smaller elements, with their quantity being selected such that sufficient torque can be transmitted to the winding core located at the exterior.

The shaft axle 501 itself may be produced entirely from fiber-reinforced plastic or may be made from a hybrid structure with fiber-reinforced plastic and metal.

LIST OF REFERENCE CHARACTERS

-   101 shaft axle -   102 cavity and/or tension bar -   103 alignment of a first layer of the continuous fibers -   104 alignment of a second layer of the continuous fibers -   201 shaft axle -   202 cavity and/or tension bar -   203 alignment of a first layer of the continuous fibers -   204 alignment of a second layer of the continuous fibers -   301 shaft axle -   302 cavity and/or tension bar -   303 aligned continuous fibers -   401 shaft axle -   402 bearing arrangement, fixed -   403 bearing arrangement, detachable -   501 shaft axle -   502 pneumatic hoses -   503 tension bar 

1. A shaft axle for winding up a material web, comprising a shaft body, which is made largely from fiber-reinforced plastic in order to achieve bending as high as possible, and comprising cavities, which are provided along the exterior perimeter of the shaft body, with the cavities being limited in the radial interior direction by a layer of fiber-reinforced plastic, and allowing tension bars to expand out of the cavities in the radial exterior direction.
 2. A shaft axle according to claim 1, with the fiber-reinforced plastic comprising aligned continuous fibers, which are connected via cured resin.
 3. A shaft axle according to claim 1, with the aligned continuous fibers being made from carbon fibers.
 4. A shaft axle according to claim 1, with the tension bars showing cup-shaped elements at their radial end, made from plastic and/or a fiber-reinforced composite material.
 5. A method for producing a shaft axle according to claim 1, with formed bodies being provided to accept tension bars that can expand radially and continuous fibers being layered around them, with the formed bodies in the radial interior direction resting at least on one layer with aligned continuous fibers, in which the formed bodies are connected to the continuous fibers is the cured resin, and in which after the resin has cured the radially expandable tension bars can be inserted into the formed bodies.
 6. A method for producing a shaft axle according to claim 1, in which a shaft body is produced largely from a fiber-reinforced plastic to yield bending stiffness as high as possible, in which cavities are cut into the shaft body along the perimeter, with the cavities in the radial interior direction being limited by a layer of fiber-reinforced plastic, and in which the tension bars that can radially expand being inserted into the cavities.
 7. A winding device for winding up a material web, comprising a shaft axle according to claim 1, showing a bearing arrangement arranged at least at one side of the shaft axle, in which the respective end of the shaft axle rests with two sections distanced from each other.
 8. A winding device according to claim 7, comprising bearing arrangements located at both sides of the shaft axle, with the ends of the shaft axle being supported therein, with each of the two bearing arrangements supporting the corresponding end of the shaft axle in two sections distanced from each other.
 9. A winding device according to claim 7, comprising at least one winding core encompassing the shaft axle, which can be fixed in reference to the shaft axle via tension bars that can expand. 